News Review From Harvard Medical School -- U.S. Malaria Cases Highest Since 1971

Malaria cases diagnosed in the United States reached a 40-year high in 2011, health officials report. Almost all were acquired while traveling in countries where malaria is common. Malaria symptoms often don't occur until weeks later. That's why people were diagnosed after they got home. In all, 1,925 cases were reported in 2011. That was the largest number since 1971. Cases increased 14% compared with 2010. Five people died. The Centers for Disease Control and Prevention reported the numbers. Nearly 70% of the cases were acquired in Africa. Nearly two-thirds of those came from West Africa. India was the source of the largest number of infections acquired in a single country. Few of the Americans diagnosed with malaria had taken malaria-prevention medicines while traveling. HealthDay News wrote about the report October 31.

By Mary Pickett, M.D.Harvard Medical School

What Is the Doctor's Reaction?

Worldwide, malaria is a major public health problem. Fever, muscle aches, headache and vomiting are the most typical symptoms. But malaria is dangerous as well as miserable. About 1 million to 2 million people die from malaria each year.

Mosquitoes that carry malaria are found in many parts of the world. But some of my patients are reluctant to take medicine to prevent malaria on trips, especially brief trips. They tell me they think their travel is too short to put them at risk. Some have heard about possible side effects from malaria-prevention drugs, so they choose to take a risk.

But think twice, travelers, if you are not planning to take precautions against malaria. Malaria has been on the rise.

In 2011, the most recent year for which we have counted cases, 1,925 cases of malaria were diagnosed in the United States. This number includes only people who were diagnosed in a U.S. clinic or hospital. It does not include travelers who were diagnosed and treated while they were still overseas. This was the largest number of cases in one year since 1971.

Almost all of these cases occurred in people who had been traveling. Malaria can take longer than a month to cause symptoms. This is why many cases are diagnosed in the United States. (Rare cases in 2011 came from donated blood or from work in a malaria laboratory.)

Let's look at some other data from 2011. About 70% of the people who were diagnosed after a trip had been traveling to visit friends or family. Only 6% had taken medicine that was recommended to them to prevent malaria. Some people never considered taking the medicine. Others brought medicine with them but stopped taking it for various reasons.

Most of the people who developed malaria needed to be hospitalized. Five people died of the infection.

Malaria can occur in travelers, even for people who are not traveling for long.

What Changes Can I Make Now?

If you plan travel to a part of the world where malaria is common, it is important to protect yourself against malaria. This can mean taking malaria medicines.

Most cases of malaria in travelers are acquired in India and Africa (particularly West Africa). There are about 100 countries where mosquitoes carry malaria. They include parts of:

Africa

Asia

The Middle East

Eastern Europe

Central and South America

The Caribbean

Oceania

The U.S. Centers for Disease Control and Prevention (CDC) website provides detailed information for travelers. It can be a helpful guide if you are planning a trip. The CDC guide can tell you whether or not you should consider taking malaria prevention medicine.

Anywhere you find mosquitoes, do what you can to avoid bites. In the United States, we no longer have malaria that is carried by mosquitoes. (However, we do have West Nile virus, which is also carried by mosquitoes.)

To avoid mosquito bites:

Stay indoors in the evenings and at night when mosquitoes are most active.

Use mosquito netting (bed nets). A net is more effective if you treat it with insecticide.

Use permethrin insecticide on your clothing.

Use insect repellant that contains DEET or picaridin for your skin. Picaridin products must be reapplied every few hours.

If you get an illness with high fever within several months of your trip, seek medical attention right away. Be sure to tell the doctor about your travel.

What Can I Expect Looking to the Future?

Unless new pest-control strategies or a successful vaccine can be developed, we are expecting to see an increase in malaria. One reason is climate change. With warming temperatures, infections that have been limited to the tropics will become more widespread. Besides malaria, tropical infections of concern include tick-borne encephalitis and dengue fever.

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